The Book of Clothes and Adornment
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا أَبُو الأَحْوَصِ، عَنْ عَاصِمِ بْنِ كُلَيْبٍ، عَنْ أَبِي بُرْدَةَ، قَالَ قَالَ عَلِيٌّ نَهَانِي رَسُولُ اللَّهِ صلى الله عليه وسلم أَنْ أَتَخَتَّمَ فِي إِصْبَعِي هَذِهِ أَوْ هَذِهِ . قَالَ فَأَوْمَأَ إِلَى الْوُسْطَى وَالَّتِي تَلِيهَا .Ali reported:Allah's Messenger (ﷺ) forbade me that I should wear a ring in this and that finger of mine, and he pointed to the middle finger and the next one
From Sahih Muslim, whose reports the scholars accept as authentic.